Does anyone REALLY know Google Voice?

So it was pointed out to me that when you ring my hobby Google Voice number, that it ports through to my iPhone's voicemail which lists my number. I don't want to change my iPhone voicemail, I'm satisfied with that the way it is.

I am wanting to know how to ensure that when someone calls my hobby number, that it goes to a separate mailbox. So I would be very appreciative if anyone can help me out.

For anyone who uses Google Voice, you might want to call that number from an outside source and make sure the same thing isn't happening to you.

For unknown numbers calling you, this is not possible. There is only one GV mailbox. For known callers, you can set up multiple email responses for groups that you create with their numbers. Their messages will still go to only one mailbox, BTW.

RingCentral.com has different voice responses possible, but I don't know much else about them.

I had to mess with mine to get everything working right in the four VM circumstances:
Personal #, no answer
Personal #, send to VM
Google #, no answer
Google #, send to VM

I ended up having to set GV to have the caller announce themselves to get everything routing to the right VM boxes.